[Br-].[Li+].[Br:3][CH2:4][CH2:5][CH2:6][CH2:7]Br.[CH3:9][O:10][C:11]1[CH:16]=[C:15]([O:17][CH3:18])[CH:14]=[CH:13][C:12]=1[Mg]Br>C1COCC1.[Cu]Br>[Br:3][CH2:4][CH2:5][CH2:6][CH2:7][C:14]1[CH:13]=[CH:12][C:11]([O:10][CH3:9])=[CH:16][C:15]=1[O:17][CH3:18]Commercially available copper(I)bromide (7.17 g, 50 mmol) and anhydrous lithium bromide (8.68 g, 100 mmol) were added to anhydrous THF (100 mL). Vigorous shaking gave a dark greenish solution. 11.5 mL (5.75 mmol) of this solution was added to a mixture of 1,4-dibromobutane (74.8 g, 346 mmol) in THF (90 mL). The mixture was warmed to 40 C., after which a solution of 2,4-dimethoxyphenylmagnesium bromide (115 mmol) in THF (100 mL), prepared by standard methods, was added over 45 min. The temperature was never more than 50 C. After the addition, the mixture was stirred for an additional 1 h at 50 C. The reaction mixture was allowed to reach 30 C. after which it was poured into ice water (200 mL). Effective stirring for 10 min gave a deep blue color. The mixture was extracted with diethyl ether (2×250 mL), dried (MgSO4) and evaporated. The excess of 1,4-dibromobutane was distilled off, and the residue was filtered through a short column of silica gel (hexane-EtOAC, 95:5). Evaporation gave the title compound as a colorless liquid (23.0 g): 1H NMR (CDCl3 -d) 7.00 (d, J=8.0 Hz, 1H), 6.44-6.39 (m, 2H), 3.79 (s, 6H), 3.42 (t, J=6.9 Hz, 2H), 2.56 (t, J=7.5 Hz, 2H), 1.90-1.83 (m, 2H), 1.73-1.62 (m, 2H); 13C NMR (CDCl3 - d) 159.13, 158.24, 129.90, 122.56, 103.74, 98.44, 55.30, 55.22, 33.87, 32.47, 28.56 (two overlapping carbon); MS (EI, 70 eV): m/z (rel. int.) 274/272 (M+, 100/96), 151 (54), 121 (43), 91 (14).
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